1. Field of the Invention
The invention relates to a novel lubricant composition which is suitable for preventing carburization on the inner surface of the tube blanks in the production of seamless pipes, and to processes of preventing such carburization.
2. Background Art
In modern tube rolling mills, e.g., in continuous trains (MPM-trains), the seamless pipes are formed in the main process step by rolling a prefabricated tube blank at 1200.degree. to 1300.degree. C. over a mandrel which is mounted on a mandrel bar. Under the influence of atmospheric oxygen or lubricants, numerous chemical reactions occur on the hot tube blank surface. Thus, the known scale (Fe oxides) forms with atmospheric oxygen, for example, which scale, if it is not removed, leads to damage of the pipe wall. It has been found that in rolling processes where scale formation is effectively suppressed and where the tube blanks do not come into contact with atmospheric oxygen, the phenomenon of carburization occurs. In a reaction interrelationship which has not been ultimately explained, a layer of iron carbides forms on the hot steel surface of the tube blanks in this process, which iron carbides, because of their hardness, lead in the rolling operation to damage (scratches) on the pipe inner wall.